Streaming communication is sometimes performed in which data sequences like audio visual data etc. are sequentially transmitted between terminals via a network such as the Internet. In such a case, there is a need to estimate an available bandwidth in order to determine the transmission rate of a stream before starting the communication. As representative methods, NPL 1 and NPL 2, and PTL 1 are known.
Each of the methods is for estimating an available bandwidth using probe packets. Each of the methods compares a transmission interval and a reception interval of two of the probe packets, and when the comparison shows that the reception interval is longer than the transmission interval, judging the current bandwidth to be unavailable.
In PTL 1, a transmitting terminal transmits a packet train composed of plural packets with a transmission time stamp, to a receiving terminal at a certain interval according to an inverse number of the bandwidth of which the availability is judged. The receiving terminal receives the packet train, and calculates, for each of the packets, an OWD (One Way Delay) based on the reception time and the transmission time of the packet. The receiving terminal judges whether or not the bandwidth is available for the packet train composed of packets transmitted at predetermined intervals, based on whether or not the one way delay(s) increase(s). When the one way delay(s) increase(s), the receiving terminal judges the bandwidth to be unavailable.
In NPL 2, a transmitting terminal transmits plural packets with a transmission time stamp in a packet sequence, to a receiving terminal at reduced intervals (hereinafter, this transmission scheme is referred to as Chirp). The receiving terminal observes whether or not there is an increase in the one way delay(s) as in PTL 1. The receiving terminal judges regarding, as the upper limit threshold value, the transmission bandwidth of the packet at the time at which the one way delay starts to increase (the transmission bandwidth corresponds to the product of the packet size and the inverse number of the packet transmission interval).
In PTL 1, a transmitting terminal transmits a packet similar to a packet used in the aforementioned Chirp, and a receiving terminal estimates an available bandwidth using information regarding the increase in one way delay(s).
According to these conventional approaches, it is possible to estimate the available bandwidth that is a bandwidth that can be used between two terminals connected through a network.